The present invention relates generally to electromagnetic energy collection and more particularly to devices useful in the collection and utilization of radiant energy from solar and other sources. The problems associated with the prior art schemes for the efficient utilization of solar energy are avoidance of energy loss through re-radiation (i.e., energy conservation) and avoidance of intricate, and hence costly, apparatus for tracking the sun in its apparent daily motion through the celestial sphere. For example, one attempt to solve solar energy conservation problems involves providing selective coatings on energy-absorbing surfaces and elaborate insulation of the particular energy "trap" employed for the utilization of collected energy. Another attempt involves including in the collection scheme reflective or refractive concentration apparatus to permit collection of solar energy impinging upon a relatively large area and focusing of collected energy toward a relatively small area of utilization. Most of these are mirroring and lens systems which are basically imaging systems wherein solar energy is reflected or refracted to a system focal point at which the "concentrated" energy is utilized for heating or power generation. These systems require tracking systems to follow the sun and thus are of questionable practicality for use in large solar energy collection systems which could replace or supplement conventional power systems.
Among the solutions proposed for avoidance of diurnal solar tracking is the provision of huge, but marginally efficient, mirrored surfaces. None of these systems has adequately solved the problems of energy conservation and solar tracking since solution of one problem often tends to enlarge the difficulties posed by the other. The systems permitting solar concentration by large factors generally require the most careful and frequent diurnal adjustments for solar tracking, while the systems requiring little or no diurnal adjustment generally provide the lowest factors of concentration.
The inventor and his collaborators in earlier publications have suggested non-imaging light funnels for the collection of light from high-energy particles and for greater concentration capacity than imaging systems, i.e., Review of Scientific Instruments, Vol. 37, No. 8, pp. 1094-5 (1966), ibid., Vol. 39, No. 3, pp. 419-20 (1968), ibid., Vol. 39, No. 8, pp. 1217-8 (1968), and J. Opt. Soc. Am., Vol. 60, No. 2, pp. 245-7 (1970). The similarity between such funnels and the geometry of retinal cones has been noted by the inventor in J. Opt. Soc. Am., Vol. 61, No. 8, pp. 1120-1 (1971). These publications dealt with proposals for "ideal", conical-shaped, light collectors which approach an f number equal to 0.5, a physically unrealizable limit for lens systems. The field of acceptance of conical collectors therein proposed may be represented by a right circular cone having a gradually diminishing (over about 1.degree.) external boundary cut-off. Therefore through non-imaging, the conical collector still required a tracking capability.
It is therefore an object of this invention to provide a device for efficiently collecting and concentrating radiant energy.
Another object of this invention is to provide a simple, non-imaging radiant energy collection device, useful in the collection of solar energy, which does not require a solar tracking capability.
Another object of this invention is to provide a nonimaging light collector for the collection and concentration of solar energy without solar tracking.